# Jasjeet S. Sekhon
# UC Berkeley
# nov 13, 2013
#
# version 4.1, updated for parallel (instead of the older snow package)
# Version 3, fixes a warning message on OS X
# Version 2, runs also on Windows but requires special version of snow, but no cygwin
#

library(rgenoud)
library(parallel)

NCPUS <- function(nchips=FALSE, ...)
  {
    nchips <- as.integer(nchips)
    if(!is.integer(nchips))
      stop("'nchips' must be an integer.\n")
    
    if(nchips < 0)
      stop("'nchips' must be a positive integer if it is specified.\n")


    #should we figure out how many cpus to use?
    if(nchips==FALSE)
      {
        if(.Platform$OS.type=="unix")
          {
            sys <- as.list(Sys.info())$sysname
            
            if(is.null(sys))
              {
                stop("as.list(Sys.info())$sysname returned a NULL")            
              }
            
            if(sys=="Linux" | sys=="linux")
              {
                foo <- paste("cat /proc/cpuinfo | grep processor | wc | awk '{print $1}'")
                nchips <- as.integer(system(foo, intern=TRUE))
                
              } else if (sys=="Darwin" | sys=="darwin") #this should also work for any BSD system?
                {
                  foo <- paste("sysctl hw.ncpu | head -1 | awk '{print $2}'")
                  nchips <- as.integer(system(foo, intern=TRUE))            
                } else {
                  stop("unix system not found. Please explicitly specify the number of chips you want to use.")
                }
            
          } else {
            stop("I think you are using Windows. For this OS please explicitly specify the number of chips you want to use.") 
          }
      }

    cat("...using",nchips,"CPUs on this computer.\n")

    if(.Platform$OS.type != "windows")
      {
        cl <- makeCluster(rep("localhost", nchips), type="PSOCK")
      } else {
        warning("it may not work on Windows")
        cl <- makeCluster(rep("localhost", nchips), type="SOCK")
      }
    return(cl)
  }
